In recent years, in the field of nano-processing of semiconductor devices and the like, the further miniaturization has been leading to a demand for a faster operation and a lower power consumption operation. Further, in the field of semiconductor manufacture, such as semiconductor devices with integrated functions, which are referred to as system LSIs, there has been a demand for a technique for higher precision to achieve integration.
With the background described above, an exposure device or the like used for a lithography technique for creating a pattern of a semiconductor device is becoming extremely more costly as a pattern becomes finer.
As an alternative technique of the lithography technique, which is becoming costly as described above, nano imprint is attracting attention. The devices, materials and the like used for the nano imprint are inexpensive, and yet the nano imprint makes it possible to form a fine pattern having a high resolution of approximately 10 nm.
As the nano imprint, there has been known, for example, thermal imprint whereby to transfer a concavo-convex pattern by heat using a thermoplastic resin, and an optical imprint whereby to transfer a concavo-convex pattern by ultraviolet rays using a photocurable resin.
In the case of the nano imprint described above, once a mold is made, a nano structure can be molded easily and repeatedly, thus leading to higher throughput with resultant increased economy. Further, the nano imprint is a processing technique that produces less harmful wastes, so that the nano imprint is recently being expected to find applications in a variety of fields, such as bit patterned media used with next-generation hard disks, in addition to semiconductor devices.
However, according to the nano imprint technique, if a mold is pressed against a resist (photocurable resin) in an air atmosphere, then air is sealed between a concave portion of the mold and the resist, and the air remains although the volume thereof decreases under compression, thus forming a space not filled with the resist. This leads to a problem in that accurate transfer of a mold shape is impossible.
The air taken in such a compressed state does not necessarily remain evenly in a concave portion of the mold, and interferes with the flow of the resin, causing the energy on the surface of the resin to decrease. As a result, the air remains in a bubbly state in the concave portion of the mold, so that a missing portion occurs in a pattern on a resist layer after completion of a transfer operation, thus leading to the degradation of transfer accuracy.
As a countermeasure to the above, the process for pressing a mold against a resist according to the imprint technique could be carried out in a vacuum, or the pressure used to press a mold could be considerably increased so as to decrease the volume of the air taken in.
However, carrying out the process for pressing a mold against a resist in a vacuum would require a robust operation chamber that could survive a vacuum. Further, if the pressure used to press the mold is excessively increased, then the mold itself would be deformed, making it impossible to perform transfer with high accuracy, or leading to damage to the mold and a substrate material in a worst case.
Therefore, as described in Patent Document 1, the present inventors have proposed a technique for preventing the degradation of transfer accuracy attributable to a gas, which is introduced to form an imprinting atmosphere, even when a relatively low pressure is used for pressing a mold. According to the technique, a condensable gas is supplied into an operation chamber, and the sealed condensable gas is condensed.
More specifically, the imprint for transferring concaves and convexes, which are formed on a mold, onto the layer of a resist applied to the surface of a base material or onto a supplied resist is carried out in the atmosphere of a gas that condenses at the temperature and the pressure in a concave portion when the layer of the resist enters into the concave portion formed in the mold. According to Patent Document 1, the vapor pressure of the gas at normal temperature is 0.05 MPa or more and 1.00 MPa or less.
Meanwhile, in Non-Patent Document 1, Non-Patent Document 2, and Non-Patent Document 3, the present inventors have identified the relationship between a gas flow rate (the ratio of a gas in relation to air) and the speed of charging a resist into a mold by supplying a 1, 1, 1, 3, 3-pentafluoropropane (pentafluoropropane), which is a type of condensable gas, between the resin and the mold, and have also reported that the viscosity of a resin before being cured can be decreased and the force for separating a cured resin from a mold (mold releasing force) can be decreased.
Further, the present inventors have reported in Non-Patent Document 4 that the surface roughness of a formed pattern, the mold releasing force, and the speed of charging a resist into a mold can be adjusted by carrying out nano imprint in the atmosphere of a mixture of one type of pentafluoropropane, which is a condensable gas, and a helium gas.